Fuel cell systems, which continually produce electrical energy through an electro-chemical reaction of fuel continuously supplied thereto, have been consistently studied and developed as an alternative for solving global environmental problems. The fuel cell systems may be classified into a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), a solid oxide fuel cell (SOFC), a polymer electrolyte membrane fuel cell (PEMFC), an alkaline fuel cell (AFC), and a direct methanol fuel cell (DMFC) according to the types of electrolytes used. The fuel cell systems may be applied to various applications, such as mobile power supply, transportation, distributed power generation, and the like, according to operating temperatures and output ranges along with the types of fuels used.
Among the fuel cells mentioned above, the PEMFC is applied to a hydrogen vehicle (a hydrogen fueled cell vehicle) that is being developed to replace an internal combustion engine. The hydrogen vehicle is driven by producing electricity through an electro-chemical reaction of hydrogen and oxygen and operating a motor with the electricity produced. Accordingly, the hydrogen vehicle has a structure that includes a hydrogen (H2) tank for storing hydrogen (H2), a fuel cell stack (FC stack) that produces electricity through oxidation/reduction reactions of hydrogen (H2) and oxygen (O2), various apparatuses for draining water produced, a battery that stores the electricity produced by the fuel cell stack, a controller configured to convert and adjust the electricity produced, a motor configured to generate a driving force, and the like.
The fuel cell stack refers to a fuel cell body having tens or hundreds of cells stacked in series. Additionally, the fuel cell stack has a structure in which a plurality of cells are stacked between end plates, each cell including an electrolyte membrane that divides the interior of the cell into two parts, an anode on a first side of the electrolyte membrane, and a cathode on a second side thereof. A separator is disposed between the cells to restrict flow paths of hydrogen and oxygen. The separator is made of a conductor to move electrons during oxidation/reduction reactions.
When hydrogen is supplied to the anode, the hydrogen is divided into hydrogen ions and electrons by a catalyst. The electrons produce electricity while moving outside the fuel cell stack through the separator. The hydrogen ions pass through the electrolyte membrane and move to the cathode, after which the hydrogen ions are combined with oxygen supplied from ambient air and electrons to produce water, and the water produced is discharged to the outside.
A fuel cell system includes an air shut-off valve apparatus configured to regulate supply air supplied into a fuel cell stack and exhaust air released from the fuel cell stack. The air shut-off valve apparatus includes a valve flap that is opened or closed by electrical control, and an air passage through which the supply air flows and/or an air passage through which the exhaust air flows may be opened or closed by the valve flap. When the valve flap is not operated normally due to a failure or malfunction in the air shut-off valve apparatus, air is unable to be supplied into the fuel cell stack. Accordingly, the fuel cell stack fails to generate electric power and driving power is unable to be supplied to a fuel cell vehicle.